In the drilling of bore holes into or through earth formation, such as, for example, in the drilling of oil or gas wells, utilizing a rotary drill bit, it may occur, from time to time, that the bit may be stuck in the earth formation or debris in the bore hole, either due to the caving in of the bore hole wall, or due to the formation of a key seat in the hard earth formation. When the bit is stuck, under such circumstances, it is difficult, if not impossible, to pull the drill string and bit from the bore hole. In the case of drilling by the usual rotary method, wherein the drill bit is attached to the lower end of a rotary string of drill pipe, it is the practice to rotate the drill pipe by the usual rotary table, as an upward pull is being applied to the drill pipe, to assist in the release of the stuck bit.
In the case of in-hole motor drill assemblies of the electrical or fluid motor types wherein the rotary drill bit is driven by the in-hole motor interposed between the running string and the bit, it is not, as a rule, possible to cause the bit to rotate by rotation of the running or drill pipe string or fluid conduit above the motor. The reaction torque of such in-hole motors is, generally, taken by a rotary table at the surface of the bore hole, whereby the drill pipe string can either be held stationary or, if desired, rotated to obviate the wedging of the string. However, if the bit becomes stuck in the bore hole, such in-hole motors will stall and continued rotation of the bit may not be possible, notwithstanding the availability of additional drilling fluid pressure or electromotive force. When such motor drills are stalled in the bore hole, rotation of the drill pipe string by the rotary table is ineffective to cause bit rotation, since there is no positive drive between the stator and the rotor and the bit remains wedged, or stuck, in the hole. As a consequence, when an in-hole motor drill has the drill bit stuck in the bore hole, an attempt can be made to pull the running pipe string and the motor drill from the bore hole, without rotating the bit, and various jarring devices have been utilized in the drill pipe string to assist in applying upward jarring forces to the drill pipe string and to the bit, in an effort to dislodge the latter.
In the event that the bit remains stuck, the practice has been to break the drill pipe joint above the motor drill assembly, if possible, in a known manner, whereby the drill pipe string can be retrieved to the drilling rig and, thereafter, to sidetrack the bore hole around the motor and bit which remain in the hole. Such practices result in great losses in time and costs.
Pending application Ser. No. 957,179, filed Nov. 2, 1978, now U.S. Pat. No. 4,232,751 by Trzeciak, relates to an in-hole motor drill apparatus, wherein the rotor of the motor is connected to the drill bit by a rotary drive connection, including torque transmitting members, which can enable the stator or housing of the motor, in the event that the bit becomes stuck in the hole, to positively transmit torque to the bit, in response to rotation of the drill pipe string.
In a specific form the torque transmitting members interlock to enable the application of pulling force to the bit as it is rotated by the pipe string in one direction.
More particularly, a normally disengaged rotary clutch is provided between the motor housing and the bit and is engaged when weight is applied through the motor housing, by the drill pipe string, in excess of that normally applied during the drilling of the bore hole. In this connection, it will be understood that the progression of the bore hole, as the bit rotates, during normal drilling operations, is dependent upon the thrust or weight applied to the cutting elements of the bit through the motor housing, such weight being transmitted to the in-hole motor drive shaft through a bearing which supports the drive shaft within the motor housing for rotation.
However, if the bit is stuck in soft formation, the application of additional weight may interfere with efforts to release the bit because the bit is forced deeper into the formation in which it is stuck.